DE3009760A1 - METHOD FOR PRODUCING HIGH PURITY PARTLY FLUORINATED AETHANES - Google Patents

Description

HOECHST AKTIENGESELLSCHAFT HOE 8o / F 051 Dr. SP / Pr

Process for the production of high-purity partially fluorinated Ethanes

The present invention relates to a process for the production of high-purity partially fluorinated ethanes Hydrofluorination of fluorine-containing ethylenes.

Partially fluorinated ethanes of the general formula

CF ₃ -CHXY,

where X = H or F and Y = H, F, Cl, Br or J, are due to their special chemical and physical properties for use in numerous fields of application suitable, e.g. as additives in gaseous analgesics and anesthetics, as heat exchange media or as propellant components. There is therefore interest in simple and economical production processes of representatives of this class of compounds.

The partially fluorinated ethanes mentioned are known per se and can be produced by several, mostly laboratory, processes. When fluorine-containing ethylene of the general Formula CF = CXY of high purity are available in sufficient quantities, hydrofluorination in the gas phase in the presence of a solid catalyst.

The addition of hydrogen fluoride to ethylenes containing fluorine in the gas phase with the formation of partially fluorinated ethanes according to the equation

yX X

^F 2 ^{C = C} \ ^{+ HF} ^ CF ₃ -CH

Y Ϋ

has already been described for some compounds. However, in all known fluorination processes in the gas phase requires relatively high temperatures,

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mostly above 250 ^° C., sometimes even above 400 ^° C. At these temperatures, however, undesirable side reactions inevitably occur. For example, in the case of ethylenes containing chlorine, bromine or iodine atoms, the halogen can be substituted by fluorine. Even in the partially fluorinated jlthane formed, the halogen can be displaced by the fluorine of the hydrogen fluoride at the high temperatures mentioned. This reactivity can be used to produce F-substituted compounds. For example, the compound CF ₃ CHClF from CF ₂ BrCHClF by reaction with HF at 300 ⁰ C in a chromium oxyfluoride catalyst is prepared according to US-PS 2,951,102.

In DE-OS 28 37 515 the hydrofluorination of trifluoroethylene at reaction ^{temperatures of 350 °} C. is described. A chromium oxyfluoride catalyst prepared according to British Patent 1,307,224 is used. The yields of 1,1,1,2-tetrafluoroethane are 90 to 95% of theory. The possible residence times are strictly limited and the proportion of fluorinated by-products is high.

Also on a chromium oxyfluoride catalyst 3,755,477 chlorotrifluoroethylene at 32O ⁰ C can be reacted to form a mixture according to US-PS, among others, 2-chloro-1,1,1 containing, 2-tetrafluoroethane (13% of theory). The same hydrofluorination process is carried out according to Canadian Patent 849,024 at 350 to 400 ° C; a considerable part of the starting product is not converted.

In our own experiments, the known gas-phase process for hydrofluorination on the fluorine-containing ethylenes mentioned the following side reactions were observed: isomerizations, disproportionations, oligomerizations, Polymerizations, fragmentation of the, C-C bonds as well

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Substitution, e.g. of chlorine or hydrogen for fluorine. These side reactions reduce the yields and lead to by-products, which often have to be separated afterwards with considerable effort. On the other hand are the reaction temperatures in the known processes are uneconomically high. This will also to a considerable extent the service life of the catalysts used is limited, especially when using ethylenes that contain hydrogen, Contain bromine or iodine and are therefore likely to poison the catalyst at high temperatures.

It was therefore the task of a simple, economical and environmentally friendly process for the production of high purity to create partially fluorinated Kthanen, which is possible low temperatures is feasible, proceeds with high selectivity and high yields, so in which the known side reactions play no role and that can easily be applied continuously.

A process has now been found for the production of high-purity fluorine-containing ethanes of the general formula CF ₃ -CHXY, where X = H or F and Y = H, F, Cl, Br or J, in which fluorine-containing ethylenes of the general formula CF ₃ = CXY, in which X and Y have the meaning given above, is reacted with at least the equimolar amount of hydrogen fluoride in the gas phase. The method is characterized in that one works at temperatures from 20 to 200 ⁰ C and in the presence of a chromium oxyfluoride catalyst which has been treated with hydrogen fluoride.

The one used in the process according to the invention, with hydrogen fluoride Treated chromium oxyfluoride catalyst can be prepared, for example, by reacting chromium oxide hydrates with water fluoride eoff (according to DE-AS 12 52 182) or by heating hydrous chromium trifluoride in the presence of oxygen (U.S. Patent 2,745,886).

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Those catalysts which are obtained from chromium oxide hydrate by treatment with hydrogen fluoride require an after-treatment with hydrogen fluoride only if it takes a long time, for example after a few months, for the inventive Process are used. However, if the same catalysts are used immediately after their preparation are used, an aftertreatment with hydrogen fluoride is unnecessary. For those made from chromium trifluoride However, after-treatment with hydrogen fluoride is always required for catalysts.

The aftertreatment of the chromium oxyfluoride catalysts takes place either for a longer time (more than 48 hours) with hydrogen fluoride at temperatures of 250 to 300 ^° C. or, even better, for a shorter time (approx. 5 to 10 hours) with a gas mixture containing hydrogen fluoride / contains elemental fluorine. In this case, generally diluted elemental fluorine with an inert gas and anhydrous hydrogen fluoride and introduced into a bath filled with the Chromoxidfluorid catalyst to 210 ⁰ C heated to temperatures of 150 tube.

the

The activation time depends on I history of the catalyst, and is generally from 5 to 10 hours. The rate per liter of contact material of the metered-in fluorine is expediently 0.1 to 5.0 l / h, the inert gas 1.0 to 3.0 l / h and the hydrogen fluoride 10 to 50 g / h.

Of course, the treatment with hydrogen fluoride / Fluorine not only take place simultaneously but also one after the other.

Treatment of a chromium oxyfluoride catalyst with a Mixture of hydrogen fluoride and elemental fluorine is essentially known from DE-OS 27 02 360 and is used there for reactivating catalysts that are used for chlorine-fluorine exchange reactions.

The inventive method is generally according to

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Customary catalytic gas-solid reaction carried out, by passing a gas mixture consisting of the fluorine-containing ethylene to be reacted and hydrogen fluoride through a heatable reaction tube which is filled with the above-mentioned pretreated chromium oxyfluoride catalyst passes is. The reaction tube is preferably set up vertically.

The reaction tube consists of an anti-hydrogen fluoride and elemental fluorine sufficiently resistant material, such as nickel, steel, copper or platinum, or is with a suitable inner lining, e.g. made of polytetrafluoroethylene or another suitable highly fluorinated polymer. The reaction gases that enter the reaction tube are left by washing with water or by absorption in towers with granulated sodium fluoride freed from excess hydrogen fluoride. The partially fluorinated ethane, which has been pre-cleaned in this way, is condensed in suitable cold traps.

The shape of the chromium oxyfluoride catalyst used is not critical; Usually spherical, cube-shaped or cylindrical bodies with a volume are used from 0.01 to 10 ecm.

The use of the compounds trifluoroethylene, tetrafluoroethylene, Chlorotrifluoroethylene, bromotrifluoroethylene or trifluoroiodoethylene is preferred in the process according to the invention. This gives 1,1,1,2-tetrafluoroethane, pentafluoroethane, 2-chloro-1,1,1,2-tetrafluoroethane, 1-bromo-i, 2,2,2-tetrafluoroethane or 1,2,2,2-tetrafluoro-1-iodoethane in almost quantitative yields.

To carry out the method according to the invention, the fluorine-containing ethylene in the gas state first mixed with hydrogen fluoride and then in the with the catalyst

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Sator filled reactor initiated.

The following table shows the boiling point of some of the starting products:
5

Table 1

fluorine-containing ethylene formula boiling point / 1 bar

10 1,1-difluoroethylene Trifluoroethylene 2-chloro-1,1-difluoroethylene 1-bromo-2,2-difluoroethylene

2,2-difluoro-1-iodo-ethylene 15 Tetrafluoroethylene Chlorotrifluoroethylene Bromotrifluoroethylene • Trifluoroiodoethylene

The fluorine-containing ethylenes are generally used in technical applications Purity, expediently used as free of water as possible. These starting products are after anrieh known processes can be produced in a simple manner; some representatives are also available on a technical scale, such as tetrafluoroethylene, chlorotrifluoroethylene or 1,1-difluoroethylene.

At atmospheric pressure, the throughput of fluorine-containing Ethylenes expediently about 1 to 90 1 (about 0.04 to

4 mol) per liter of catalyst and hour. At higher pressures, the throughput of fluorine-containing ethylenes can be correspondingly higher. Lower throughputs are possible, but uneconomical.
35

The process according to the invention generally takes place in

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CF ₂ = CH ₂ -82 ° C CF ₂ = CHF -61 ° C CF ₂ = CHCl -17.7 ° C CF ₂ = CHBr + 6.1 ⁰ C CF ₂ = CHJ + 34 ° C CF ₂ = CF ₂ -76.3 ° C CF ₂ = CFCl -27.9 ° C CF ₂ = CFBr - 4.5 ° C CF ₂ = CFJ +29 ⁰ C

Normal pressure instead of, but also allows the use of positive or negative pressure within wide limits. So you can at Pressure below 1 bar or at overpressure from 1 to 10 bar or more, preferably at 1 to 3 bar, work. In particular, to achieve higher space-time yields the use of positive pressure is preferable.

If the starting compounds are not anhydrous, this can lead to side reactions (formation of products containing oxygen) come.

Hydrogen fluoride is generally added without dilution. The amount of gaseous hydrogen fluoride metered in is generally between 0.8 and 250 g (or 0.04 and 12.5 mol) per liter of catalyst and hour. It should be at least the amount of the fluorine-containing ethylene used in each case be equivalent, but preferably be higher. The molar ratio of fluorine-containing ethylene to hydrogen fluoride is generally between 1: 3 and 1: 1, preferably between 1: 2 and 1: 1.1, in particular between 1: 1.5 and 1: 1.1. The total amount of hydrogen fluoride introduced is provided only an excess (based on the fluorine-containing ethylene used) is used, not critical. An excess of hydrogen fluoride is beneficial in that it gives a quantitative conversion of the fluorine-containing ethylene is achieved. Larger excesses of hydrogen fluoride are also possible; however, this increases the work-up effort. Excess hydrogen fluoride is removed from the reaction gas either by washing with water or dilute sodium hydroxide solution removed or absorbed in towers with granulated sodium fluoride at room temperature. Because the hydrogen fluoride thermally again after absorption by sodium fluoride can be desorbed and reused, the losses of hydrogen fluoride remain very small in this mode of operation. Work-up by fractional distillation is also possible.

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In general, the reaction is carried out without the addition of an inert gas. Dilution, for example with nitrogen or another inert gas, is possible, but only brings about a minimal increase in the yield.
5

The reactions are carried out at temperatures of 20 to 200 ⁰ C, advantageously at 40 to 19O ⁰ C, especially at 60 to 180 ⁰ C.

The residence time of fluorine-containing ethylene or the resulting fluorine-containing ethane in the reactor is not
critical. You can choose between a few in both cases
Seconds and a few minutes sway; it is only limited at the top by economic considerations. It

is a particular advantage of the method according to the invention consider that the residence time can be varied within wide limits without affecting the composition of the reaction product is influenced by it.

In the process according to the invention, a continuous procedure, ie continuous introduction of the starting materials, continuous recycling of the excess hydrogen fluoride and continuous isolation of the
partially fluorinated ethane formed easily possible. Particular advantages of the continuous mode of operation are the high utilization of the starting materials used and the low amount of waste water and exhaust gas.

The conversion of the fluorine-containing ethylene used is in the process according to the invention in general at over 95%, but often at 99-100%.

Because of the high selectivity of the process according to the invention, the yields are partially fluorinated ethanes
also over 95%, but often over 98%. Thus, the ethanes are obtained in a high degree of purity. Proves to be beneficial

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the process according to the invention is mainly in that side reactions are almost completely suppressed and The work-up thus proves to be extremely simple.

The following table gives the boiling points of the partially fluorinated Ethanes again, which can be produced from the fluorine-containing ethylenics in Table 1.

Table 2: Ethanes

description

formula

Boiling point / 1 bar

1,1,1-trifluoroethane 15 1,1,1,2-tetrafluoroethane 2-chloro-1,1,1-trifluoroethane, 1-bromo-2,2,2-trifluoroethane 2,2,2-trifluoro-1-iodoethane Pentafluoroethane

20 2-chloro-1,1,1,2-tetrafluoroethane

.1-Bromo-1,2,2,2-tetrafluoroethane

1,2,2,2-tetrafluoro-1-iodine-25 ethane

CF3-CH3 -47 ,8th ⁰ C CF ₃ -CH ₂ F -26 , 5 ⁰ C CF ₃ -CH ₂ Cl + 6 /1 ⁰ C CF ₃ -CH ₂ Br +26 ⁰ C CF ₃ -CH ₃ J +55 ⁰ C CF ₃ -CHF ₂ -48 , 5 ⁰ C CF ₃ -CHClF -12 ⁰ C CF ₃ -CHBrF + 7 ⁰ C CF ₃ -CHFJ + 39 ⁰ C

From DE-OS 27 12 732 it is known, that perfluoropropylene ^{reacts with hydrogen fluoride at temperatures from 100 to 35O 0} C in the presence of chromium oxyfluoride catalysts. The yields of 2H-heptafluoropropane at reaction ^{temperatures below 200 °} C. are only moderate. ^{At 160 to 170 °} C., for example, they are only 82% of theory. In addition, the importance of the pretreatment of the catalyst with hydrogen fluoride is not apparent from this reference.

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It is surprising that the hydrofluorination occurs in the presence of the chromium oxyfluoride catalysts aftertreated with HF of fluorine-containing ethylenes with high conversions, often quantitative, and with extremely high selectivity. In particular Surprised that the reaction temperatures of the process according to the invention compared to the prior art Technology are unexpectedly low.

The method according to the invention represents a considerable Technical progress as it is available on the basis of either technically available or beyond other technical Intermediate products of readily available fluorine-containing ethylenes with optimal utilization of the starting materials, without substantial formation of isomerization-disproportionation-, Oligomerization, polymerization, fragmentation or substitution products, the production of partially fluorinated ethanes in yields of over 95%, sometimes up to 99%. Associated with it a simple work-up and an easily achievable high degree of purity of the end products. Furthermore, the inventive Process due to the low reaction temperatures and the associated long service life of the used Catalysts of great interest.

The process is explained in more detail by the following examples: Example 1

Activation of chromium oxyfluoride catalysts with hydrogen fluoride or with a gas mixture of hydrogen fluoride and elemental fluorine and the subsequent hydrofluorination of the fluorine-containing ethylenes were carried out in the same test facility.

This consists of a vertical nickel tube with a length of 150 cm and an inside diameter of 5 cm.

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- K-

The reactor is heated from the outside with a heating jacket; A VA steel tube with an outer diameter of 0.6 cm, an inner diameter of 0.4 cm and a length of 145 cm runs axially inside the reactor tube, through which a thermocouple can be inserted to measure the internal temperature at any desired reactor height . The granular catalyst material is held at the desired height of the tube through a sieve part fitted inside the reactor tube. At the lower end of the reactor there is a separately heatable nickel vaporizer into which the pipelines for gaseous hydrogen fluoride, diluted or undiluted fluorine gas and for gaseous fluorine-containing ethylene (in example 1: 1,1-difluoroethylene) lead. The evaporator vessel is kept at a temperature between the boiling point of hydrogen fluoride (+20 ⁰ C) and the reactor temperature. A pipeline leads from the upper end of the nickel reactor into a washing receptacle filled with water, in which hydrogen fluoride which has not reacted during the hydrofluorination is collected and titrated on a trial basis. In the case of activations with elemental fluorine, a receiver with hexafluoropropylene is connected between the reactor outlet and the washing vessel. Excess fluorine can thus be safely absorbed (cf. DE-OS 23 32 097); additional fluorine tests are carried out during the activations with potassium iodide paper.

Elemental fluorine (F ₂ ) is taken from a commercially available steel bottle, measured with a previously calibrated differential pressure flow meter and, after dilution with nitrogen, passed into the reactor. In front of the fluorine flow meter, a riser manometer, which also serves as a safety valve, is attached to monitor the dynamic pressure that is being established. The dynamic pressure gauges are filled with perfluorinated polyether oils.

Hydrogen fluoride (HF) is sold with over 99%

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usual purity and with a basically similar measuring arrangement, as described for fluorine, dosed. In addition, radiant heaters are attached to prevent condensation of HF in the pipes up to the evaporator to prevent.

600 ml (bulk volume) of a chromium oxyfluoride catalyst which had been prepared by fluorinating chromium oxide hydrate green with hydrogen fluoride according to DE-AS 1,252,182 are placed in the reactor tube. For activation, the initially charged catalyst is treated at an internal temperature of 190 ^° C. for 10 hours with a gas mixture consisting of 0.35 l / h fluorine, 0.5 l / h nitrogen and 15 g / h hydrogen fluoride; it is then rinsed with 15 g / h of hydrogen fluoride at the same internal temperature for 5 hours.

The 1,1-difluoroethylene is taken from a standard steel bottle. For hydrofluorination at reactor temperatures of 80 ⁰ C (at the beginning) to 98 ° C (after occurrence of the exothermic addition reaction) to the activated Chromoxyfluoridkatalysator within 6 hours a total of 420 g (6.56 mol) of CF ₂ = CH ₃ and 237 g ( 11.85 mol) HF, corresponding to a molar ratio of CF ₂ = CH ₂ : HF such as 1: 1.81.

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5.23 moles of HF are collected in the wash water. The gaseous reaction product is passed through a CaCl ₃ drying tower for drying and then condensed in an intensive trap cooled with solid carbon dioxide. The gas chromatographic measurement of this crude product on an ORAPAK column gives the following composition:

35

CF ₃ -CH ₃ < 99.6% CF ₂ = CH ₂ 0.3% CHF ₃ 0.05 CH ₂ F ₂ 0.05

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CHF ₂ -CH ₃

The condensed crude product weighs 537 g. The yield of CF ₃ -CH ₃ is thus 97.3% of theory. ₍ based on converted CF ₀ = CH. A further identification of 1,1,1-trifluoro-

19 1 ethane is carried out by infrared, F and H-NMR spectra.

The boiling point of the product is -48 to -47 ° C.

Example 2

In the experimental arrangement from example (1), a total of 235 g (2.87 mol) of CF ₂ = CHF, which has been prepared by dehalogenation of CBrF ₂ -CHClF, and 83 g (4.15 mol) of HF, corresponding to a molar ratio of CF ₂ = CHF: HF such as 1: 1.45, passed.

1.25 mol of HF are titrated in the wash water. The gas chromatographic Uptake of the crude product caught in the trap gives the following values:

CF ₃ -CH F 99.7 CF ₂ = CHF <. ° ^'05 CHF ₃ <0.05 CF-CH ₃ <C 0.05

The condensate weighs 286.5 g; thus the yield of 1,1,1,2-tetrafluoroethane is 97.6% of theory. based on converted CF ₀ = CHF. The characterization of 1,1,1,2-tetrafluoroethane

19 1
is carried out by IR, F and H-NMR measurements; the boiling point is -27 ° C to -26 ° C.

Comparative example 1
35

In the experimental setup from example (1), 600 ml

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Submitted (bulk volume) of a chromium oxyfluoride catalyst which has been prepared according to DE-AS 1,252,182. In this case, the catalyst material is initially only pretreated with hydrogen fluoride; at temperatures of 330 ^° C. to 350 ^° C. in the course of 72 hours, a total of 1080 g of HF are passed over the initially charged catalyst at a rate of 15 g / h.

Over the prepared catalyst in the manner described at temperatures from 125 to 142 ⁰ C within 3 hours a total of 243 g (2.96 mol) of CF ₂ = CIIF and 86 g (4.30 mol) of HF, corresponding to a molar ratio of CF ₂ = CHF: HF as 1: 1.45 directed.

1.45 moles of HF are collected in the wash water. The condensed crude product settles according to a gas chromatography Measurement as follows:

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CF ₃ -CH ₂ F 95.8 CF ₂ = CHF 4.0 CHF ₃ < 0.05 CF ₃ CH ₃ <f 0.05

The crude product has a weight of 2 93.5 g; Based on converted CF ₂ = CHF, the yield of CF ₃ -CH ₃ F is 97% of theory, but the conversion of CF ₃ = CHF is only about 96%.

Example 3

In the Versuchsanordmmg from Example (1), the catalyst used in Comparative Example (1) for activation - as described in Example (1) - at an internal temperature of 190 to 195 ° C for 10 hours with a gas mixture consisting of 0.35 l / h fluorine, 0.5 l / h N ₃ and 15 g / h HF, pretreated. It is then used at 190 ^° C. for 5 hours

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15 g / h HF rinsed.

Prepared using the method described in the manner Chromöxyfluorid catalyst is at an internal temperature of 75 ⁰ C (at the beginning) to 96 ⁰ C (by heat of reaction caused), a gas mixture within 26 hours, consisting of a total of 1698 g (20.7 mol ) CF = CHF and 666 g (33.3 mol) of HF at a molar ratio of CF ₂ = CHFrHF such as 1: 1.61.
10

12.55 moles of HF are found in the wash water. The gas chromatographic Measurements show the following composition for the collected crude product:

CF ₃ -CH ₂ F 99.8% CF ₂ = CHF < 0.05% CHF ₃ <~ 0.05% CF ₃ -CH ₃ <Γ 0.05%

The condensate weighs 2088 g; thus the yield of CF ₃ —CH ₂ F is about 99% of theory, based on converted CF ₂ = CHF, which in this example could be converted quantitatively at very moderate temperatures.

Example 4

In the experimental apparatus of Example (1) catalyst oxyfluoride is the used in Comparative Example (1) at an internal temperature of 120-131 ⁰ C within 6.0 hours, a gas mixture consisting of a total of 510 g (5.18 mol) of 2 -Chlor-1,1-difluoroethylene, which has been prepared by dechlorinating 1,1,2-trichloro-2,2-difluorathane, and 153 g (7.65 mol) HF with a molar ratio of CF ₃ = CHClrHF as 1 : 1.48, conducted.

2.33 mol HF and 0.04 mol HCl are titrated in the washing water,

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According to the gas chromatographic investigations, this exists Raw product from the following components:

CF ₃ -CH ₂ Cl 99.0%

CF ₂ = CHCl <^ 0.05%

CF ₃ -CH ₂ F 0.8%

CF ₃ -CH ₃ <C 0.05%

The crude product collected has a weight of 603 g; thus the yield of 2-chloro-1,1,1-trifluoroethane obtained is 97.2% of theory, based on converted CF ₉ = CHCl. The ethane CF_-CH "C1 obtained was additionally obtained by uptake

19 T
of IR, F and H-NMR spectra as well as determination

the boiling point of +6 ⁰ C to +6.5 ⁰ C characterized. 15th

Example 5

For the hydrofluorination of tetrafluoroethylene, which is used in the high purity required for polymerizations, 600 ml (bulk volume) chromium oxyfluoride catalyst is _{pretreated with a gas mixture consisting of F ", HF and N 2} in the apparatus used in Example (1), as in Example (1) described.

A total of 370 g (3.70 mol) of CF ₃ = CF ₂ and 170 g (8.5 mol) of HF, corresponding to a Molar ratio of CF ₉ = CF ₉ : HF such as 1: 2.3.

4.95 moles of HF are collected in the wash water. The gas chromatographic Analysis shows the following values for the raw product obtained:

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CF ₃ -CHF ₂ 92.5%

^ - f 2 ~ 2

CHF ₃ 0.2%

CF ₃ -CF ₃ 0.25%

CyClO-C ₄ F ₈ / ν 1%

The condensate obtained weighs 417 g; thus the yield of pentafluoroethane is approx. 93% of theory, based on converted CF ₂ = CF ₃ . Pentafluoroethane CF ₃ -CHF ₂ was further characterized by IR and NMR measurements. A subsequent low-temperature distillation gave a fraction of 372 g in the boiling range from -49 to -47.5 ° C. / normal pressure, consisting of pentafluoroethane to an extent of more than 99%.

Comparative example 2

In the experimental arrangement of Example (1), filled with the chromium oxyfluoride catalyst of Example 5, at a temperature of 280 ⁰ C to 288 ⁰ C within 3.0 h total of 202.5 g (2.03 mol) of CF ₃ = CF ₂ and 113 g (5.65 mol) of HF, corresponding to a molar ratio of CF = CF ₂ : HF such as 1: 2.8.

4.05 moles of HF are found in the wash water. From the gas chromatographic Measurement of the collected raw product shows the following:

CF ₃ -CHF ₂ 83.5%

CF ₂ = CF ₂ <0.05%

- CF ₃ -CF ₃ 3.5%

CyCIo-C ₄ F ₈ 3.3%

C ₆ F ₁₂ 8.5%

Furthermore, white, solid residues consisting of polytetrafluoroethylene are observed on the catalyst material. With a weight of 184 g for the condensate (raw product)

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the yield of pentafluoroethane in this comparative example is only about 63% of theory, based on converted CP ₂ = CF ₃ . An increase in the reactor temperature leads to a quantitative conversion of ethylene, but causes a higher proportion of by-products.

Example 6

For the hydrofluorination of chlorotrifluoroethylene, which is used as a technical Intermediate product is readily available in high purity, in the experimental apparatus from Example (1) the im Comparative example (1) submitted chromium oxyfluoride catalyst used.

At an internal temperature of 170 to 178 ° C., a total of 605 g (5.19 mol) of CF ₂ = CFCl and 152 g (7.6 mol) of HF, corresponding to a molar ratio of CF ₂ = CFClrHF as in 1, are obtained within 6.5 hours : 1.46, reacted in the reactor tube.

2.48 mol of HF and 0.03 mol of HCl are titrated in the wash water. The composition of the raw condensate is based on a GC measurement established:

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CF ₃ -CHClF 95.6 CF ₂ = CFCl 3.0 CF ₃ -CHCl ₂ 0.4 CF ₃ -CHF ₂ 0.8 CF ₃ -CH ₂ Cl <0.1 CF ₃ -CClF ₂ <0.1

No polymers were observed. The collected crude product weighs 669 g; thus the yield of CF ^ -CHClF is 93.1% of theory, based on converted CF ₀ = CFCl.

19 The further characterization is carried out by IR and F and H-NMR measurements. A subsequent low-temperature distillation gives a fraction ^{at -12.5 to -11 0 C}

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a weight of 612 g of pure 2-chloro-1,1,1,2-tetrafluoroethane.

Comparative example 3
5

In the experimental apparatus of Example (1) filled with the catalyst of Comparative Example (1), at an internal temperature of 270-280 ⁰ C within 4 hours a total of 354 g (3.04 mol) of CF ₂ = are CFCl and 92 g ( 4.6 mol) HF, corresponding to a molar ratio of CEsCFCIrHF of 1: 1.51.

1.19 moles of HF and 0.33 moles of HCl are collected in the wash water. The crude product is composed as follows according to GC analysis:

CF ₃ -CHClF 20.7 CF ₂ = CFCl <0.05 (A) CF ₃ -CHCl ₂ 29.6 (B) CF ₃ -CHF ₂ 41.0 (C) CF ₃ -CH ₂ Cl 4.5 (D) CF ₃ -CClF ₂ 4.2

The formation of products (A) and (B) or (C) and (D) can be explained by the various possibilities of disproportionation of CF - CHC1F formed; the higher proportion of product (B), pentafluoroethane, arises from chlorine-fluorine exchange in the CF ₃ -CHClF. This comparative example clearly shows the determining influence of the reactor temperature on the composition of the reaction products.

Example 7

For the hydrofluorination of Bromtrifluoroäthylen is in the Experimental apparatus from example (1), filled with a cata-

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τη _

lysator as described in Example (1), at a temperature of 165 to 176 ° C within 4 hours, a gas mixture consisting of a total of 334 g (2.07 mol) of CP ₂ = CFBr and 110 g (5.50 mol) of HP (Molar ratio of CF ₂ = CFBr: HF such as 1: 2.66) implemented.

3.44 moles of HF are collected in the wash water. The GC analysis of the raw product results in:

CF ₃ -CHBrF < 94.5 CF ₂ = CFBr 3.0 CF ₂ Br-CHF ₂ 1.1 CF ₃ -CHF ₂ 1.0

356 g of crude product collected in the trap. The yield of CF ₃ -CHBrF is about 93% of theory, based on converted CF "= CFBr. The purified crude product was determined by IR and NMR measurements and by determining the boiling point from +7 to 7.5 ° C characterized.

Example 8

For the hydrofluorination of trifluoroiodoethylene, which can be prepared, for example, by dehydrochlorination of 2-chloro-1,2,2-trifluoro-1-iodoethane according to known methods, the experimental apparatus from Example (1) is filled with the catalyst from Example ( 1), used. A total of 249 g (1.20 mol) of CF ₂ -CFJ and 46 g (2.3 mol) of HF (corresponding to a molar ratio of CF ₂ = CFJrHF like 1: 1.9).

1.03 mol of HF are titrated in the wash water. The GC analysis of the raw condensate results in the following composition:

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CF 3 -CHFJ 2 < 93.5 % CF 2 = CFJ J 2.5 % CF 3 -CHF ₂ 1.1 % CF 2 J-CHF 1rO % CF 2 J-CF ₂ 1 %

The collected crude product weighs 268 g; thus the yield of CF ₃ -CHFJ obtained is approx. 94% of theory, based on converted CF ₉ = CFJ. The main product obtained was

19 1

further characterized by IR, F and H-NMR measurements. The boiling point of ethane is + 39 ° C / 1 bar.

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Claims (5)

HOE 8O / F 051 Patent claims: (1st! Process for the production of highly pure fluorine-containing ^ - ^ ethanes of the general formula CF ₇ - CHXY where X = H or F
and Y = H, F, Cl, Br or iodine means _{ from fluorine-containing ethylenes of the general formula CF ₂ = CXY, in which X and Y have the meaning given above with at least the equimolar amount of hydrogen fluoride in the gas phase, characterized in that one works at temperatures of 20-200 ⁰ C and in the presence of a chromium oxyfluoride catalyst which has been treated with hydrogen fluoride.
15th 2. The method according to claim 1, characterized in that the chromium oxyfluoride catalyst additionally with elemental Fluorine has been pretreated. 3 · The method according to claim 2, characterized in that the chromium oxyfluoride catalyst is pretreated with a gas mixture containing fluorine and hydrogen fluoride became. 4. The method according to any one of claims 1 to 3, characterized in that at reaction temperatures of 40 ° - 190 ⁰ C, working in particular 60-180 ⁰ C. 5. The method according to any one of claims 1 to 4, characterized in that the molar ratio is fluorine-containing Ethylene to hydrogen fluoride is 1: 1 to 1: 3. 130039/0377